1. Field of the Invention
The present invention relates to a further improvement in the conversion of methane to higher boiling hydrocarbons using adiabatic thin bed reactors, wherein a certain amount paraffin hydrocarbon having 2 or more carbon atoms is incorporated in the feed gas.
2. Description of the Prior Art
Methane is found in large quantities in gaseous form in somewhat remote regions of the world. The transportation of this methane to areas where it can be utilized is relatively inefficient.
Considerable work has been carried out relating to the conversion of methane to higher hydrocarbons which are readily condensable and which can be conveniently transported in liquid form. In this regard, reference is made to the following U.S. patents which are concerned with conversion of methane to higher hydrocarbons: U.S. Pat. Nos. 4,443,649; 4,444,984, 4,443,648, 4,443,645; 4,443,647; 4,443,644; 4,443,646; 4,499,323; 4,499,324; 4,593,139; 4,489,215; 4,499,322; 4,495,374; 4,544,784; 4,544,785; 4,547,610; 4,547,611; 4,517,398; 4,544,787; 4,547,608; 4,544,786; 4,568,785; 4,523,049; 4,523,050 and the like.
The conversion of methane to higher hydrocarbons in the presence of solids which may contain oxidative synthesizing agents as described in the above patents takes place effectively at elevated temperatures in the range of about 500.degree. C. to 1200.degree. C. The reaction is strongly exothermic in nature, and in order to properly regulate the reaction and prevent excessive undesirable side reactions, it is necessary to remove the exothermic heat of reaction to avoid an exessive temperature rise, and to rapidly lower the temperature of the reaction product mixture.
Problems particular to this conversion of methane include the fact that the reaction temperature is high enough to preclude or bring into serious question the use of many materials normally used in reactor construction.
The high temperatures result in rapid conversion of the reaction products to undesirable materials unless the residence time of the products at elevated temperatures is very short. Thus, high reaction space velocities and rapid quenching of the product are desirable.
Fixed bed reactors of the tubular or massive bed configuration have been considered for the reaction However, such systems have not been satisfactory due to their cost and complexity, to pressure drop and materials of construction problems and to problems of heat removal and effluent quenching.
A further disadvantage of conventional fixed bed reactors is that the feed must be preheated to elevated temperatures. This requires fuel as well as an expensive ceramically lined furnace.
Copending applications Ser. Nos. 07/031,496 filed Mar. 30, 1987 and 07/158,128 filed Mar. 4, 1988 describe thin bed adiabatic systems for successfully carrying out the methane conversion. It is a feature of the present invention that enhanced flow rates in a thin bed system can be achieved.